Nemo is described as "the hardened leader of the Nautilus submarine, who's a zealous believer in a cause that takes him from 20,000 leagues under the sea to the destiny that he won't let anyone prevent him from achieving." He also has ties to Captain Hook (Colin O'Donoghue), though whether they are friends or foes is uncertain.

"We're thrilled to give a 'Once Upon a Time' spin to the classic character of Captain Nemo from one of our favorite Disney films, '20,000 Leagues Under the Sea,'" executive producers Adam Horowitz and Edward Kitsis said. "We're excited to see his mythology merge with Storybrooke's own captain -- Hook. If for no other reason than to see the Jolly Roger go up against a submarine."

Horowitz and Kitsis have previously teased more flashbacks to Hook's past, so it's possible that he and Nemo had a run-in on the sea. Or perhaps Nemo is a denizen of the Land of Untold Stories, a new realm seen at the end of last season.

Nemo won't be the only new character coming to Storybrooke -- the show is also introducing Aladdin (Deniz Akdeniz), Princess Jasmine (Karen David), Jafar (Oded Fehr), Morpheus (Giles Matthey), and the Count of Monte Cristo (Craig Horner).

"Once Upon a Time" Season 6 premieres Sunday, Sept. 25 at 8 p.m. on ABC.